Autopsy results show a mother apparently killed her two young daughters before turning the gun on herself inside the family's high-end home, police said Monday. Nina Obukhov, 34, killed her daughters...

UPDATED: Manchester police officer charged with Bedford hit-and-run

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UPDATE: Former Manchester Sgt. Stephen Coco, turned himself in on two felony warrants charging him with conduct after an accident and was arraigned early Tuesday morning in 9th Circuit Court District Division in Merrimack.

Hillsborough County Attorney Patricia LaFrance, at a press conference this morning at Bedford Police Department, said two teenage boys, ages 17 and 18, were struck from behind by an undercover police vehicle allegedly operated by Coco near 31 Harrod Lane. Coco was off duty at the time, LaFrance said.

LaFrance said a mugshot for Coco will not be released as doing so might post a risk to him as a former undercover officer assigned to the Special Investigations Unit.

Coco, 41, of Bedford lives about a mile away from the accident scene, she said. Both teens were released from the hospital and are recovering from their injuries.

Coco was fired Monday after an internal investigation conducted by Manchester police revealed he had violated several of the department's standard operating procedures, according to Manchester Police Chief David Mara.

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Earlier article continues below in full.

BEDFORD — The county's top prosecutor said she hopes an arrest warrant will be issued in the next two days in connection with a hit-and-run accident Friday night involving a Manchester police undercover vehicle.

Meanwhile, Manchester police announced that police Sgt. Stephen Coco, a 17 1/2-year veteran on the force, had been fired from his $84,000-a-year job Monday afternoon following an internal investigation into the accident. Police Chief David Mara said Coco, a member of a drug investigation unit, had been assigned the vehicle involved in the accident.

An internal affairs investigation found Coco had violated several police procedures, Mara said.

The hit-and-run accident took place about 9:20 p.m. Friday on Harrod Lane, a quiet residential street of about a dozen homes in south Bedford. Two pedestrians were injured, one with what Bedford police initially described as "serious head trauma."

Hillsborough County Attorney Patricia LaFrance said a 17- and 18-year-old male were both treated at a hospital, but have since been sent home.

"They're both very fortunate they did not sustain life-threatening injury," LaFrance said.

She said her office is consulting with Bedford police, which is investigating the accident. Information about the accident will be released once an arrest warrant is issued. LaFrance said she hopes an arrest will be made within a couple of days, but stressed it depends on the pace of the investigation.

"This case, obviously because it involves an off-duty Manchester police officer, we want to make sure people understand there's no favoritism. We're investigating this as we would any conduct-after-an-accident and we want the public aware of that," she said.

Once an arrest is made, LaFrance plans to refer the case to a prosecutor outside of Hillsborough County to avoid any perception of favoritism, she said.

State law makes it a felony not to report an accident that results in bodily injury.

LaFrance on Monday would not name the victims or discuss their injuries. She would not say whom authorities believe was driving the vehicle. Nor would she say how many people were in the vehicle.

She said the vehicle has been impounded by Bedford police. LaFrance said police are also investigating why the vehicle was in the neighborhood at the time.

This is not Coco's first involvement with Bedford police. In 2004, authorities investigated his shooting and killing of an unleashed Belgian shepherd-chow mix after he said it rushed at him and his two pre-school-age daughters in Pulpit Rock Park in Bedford.

Coco shot the dog three times with his service-issued, .40 caliber handgun. An investigation cleared him of any crime in the shooting.

Mara said an internal investigation was opened early Saturday morning.

The unmarked, undercover vehicle was assigned to Coco, Mara said. He said Manchester police are cooperating with Bedford police in their investigation into the accident.

Manchester police, he said, are "greatly saddened to learn of this terrible incident and our thoughts and prayers remain with the victims and their families."